Listeria innocua infection in an old case of total knee replacement – an unusual case report

Prosthetic implant-associated arthritis due to Listeria is mostly reported for Listeria monocytogenes. Here, we describe a patient who underwent total knee replacement 12 years ago and presented with pain, tenderness, redness and local rise in temperature in the right knee. Purulent fluid was aspirated. Upon microbiological analysis, culture yielded Listeria innocua. L. innocua is rare. Listeria is not reported as a contaminant and routine cultures may be negative. Because of the long interval between surgery and the onset of symptoms, clinical suspicion, radiological investigations and analysing multiple samples are of immense help.


INTRODUCTION
Listeria, a Gram-positive bacillus, is believed to be pathogenic and is associated with invasive diseases such as foodborne listeriosis, meningitis and bacteraemia, usually in immunocompromised individuals [1].Listeria is ubiquitously present in moist environments, soil, water and decaying vegetation.Bone and joint infection due to Listeria are quite rare and are mostly reported for Listeria monocytogenes [2,3].Another species, Listeria innocua, has even more rarely been associated with human disease [4].We report a case of joint infection due to L. innocua in an old case of total knee replacement.

CASE PRESENTATION
An older female patient with a 3 month history of right knee discomfort, redness and oedema reported to the orthopaedic outpatient department (OPD).This patient has been a known diabetic for the last 20 years with fair blood sugar management.Local examination revealed swelling of the right knee with mild erythema and local rise of temperature over the right knee, which was tender on palpation with slight restriction in movement.Twelve years previously, the patient underwent bilateral total knee replacement (TKR) surgery.Before this occurrence, there was no prior history of the same symptoms after surgery.Blood test results showed TLC 12 000 mm −3 , ESR 82 mm first hour and CRP 68 mg dl −1 .No abnormality was seen on the AP or lateral X-ray of either knee.Cefuroxime 500 mg twice daily was started empirically with significant response.After 15 days, blood tests showed a >6× drop in ESR (12 mm first hour) and an 18× drop in CRP (3.74 mg dl −1 ).With this, the patient again presented to OPD after 3 weeks with mild pain and swelling.On examination there was mild tenderness over the right knee joint line with mild effusion but no erythema.Thick straw-coloured turbid fluid was aspirated and subjected to cytological, biochemical and microbiological analysis.ESR and CRP were also raised again to 101 mm first hour and 12.18 mg dl −1 , respectively.
On fluid analysis, the total cell count was 26000 mm −3 with predominant polymorphonuclear cells, high LDH 1451.7 U l −1 with protein 6.3 gm dl −1 and no micro-organism on Gram stain.The fluid was inoculated in a Bact Alert FA bottle (bioMérieux, Inc., USA) and incubated in Bact Alert, which is an automated blood culture incubation instrument, at 37 °C and showed positive growth after 2 days of aerobic incubation.Upon subculture, growth revealed non-haemolytic, non-lactose-fermenting fine colonies of Gram-positive rods (Fig. 1).This was identified as L. innocua by VITEK 2 (bioMérieux, Inc., USA) and found to be susceptible toward extended-spectrum penicillin, aminoglycosides, macrolides and fluoroquinolones.
The patient was treated conservatively with a combination of ampicillin, 500 mg, 6 hourly, and gentamicin, 1 mg kg −1 , IV for 2 weeks.On the first follow-up, which was 13 days after the initiation of antibiotics, ESR and CRP had fallen to 71 mm first hour and 4.26 mg dl −1 , respectively, which further decreased to 58 mm first hour and 1.19 mg dl −1 , respectively, at the second follow-up after 35 days (Table 1).The patient also improved symptomatically and on follow-up there was no recurrence.

DISCUSSION
Gram-positive cocci such as Staphylococcus and coagulase-negative Staphylococcus are the most important aetiological agents for hip and knee prosthetic and periprosthetic joint infections, accounting for 50-60 % of cases.Gram-negative bacteria and other atypical organisms are now recognized as causative agents in immunocompromised individuals, with an upsurge in joint replacements [5,6].One such unusual agent is the genus Listeria in which Listeria monocytogenes is usually associated with rare bacterial diseases such as listeriosis, caused by contaminated food stored for long periods at a low temperature, sepsis and meningoencephalitis.This can cause serious illness in pregnant women, neonates, the elderly and immunocompromised individuals.The incubation period varies from a few days to 3 months.
Listeriosis on rare occasions may manifest as local infections in different organs such as bones and joints [7].It may lead to septic arthritis involving prosthetic devices.The first case was reported way back in 1980 by Neiman and Lorber [8].Endocarditis associated with prosthetic valves, endophthalmitis and lymphadenitis were also reported [9][10][11][12][13][14]. Due to the unusual nature of the bacterium, its rarity of isolation and identification and the relatively lengthy time between surgery and the onset of symptoms, the association between Listeria and arthritis is less well known.Sometimes, symptoms may not be that evident or incapacitating because of latent or subclinical infection.Case series and isolated reports have been published about L. monocytogenes with prosthesis, but there are only two case reports (one of bacteraemia and a second for neonatal meningitis) involving Listeria innocua, reported in 2003 and 2014 [15,16].To the best of our knowledge, this is the first report for a case of prosthetic joint infection due to L. innocua.This case study is unique in describing a rare aetiology for an infection in a very old case of a total knee replacement.No revision surgery or implant removal was required, since the patient was managed conservatively and responded to antibiotics.It probably presented as an indolent low-grade infection.The Microbiology Society is a membership charity and not-for-profit publisher.
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Find out more and submit your article at microbiologyresearch.org Response 1. Listeria is widely accepted as a pathogen.I suggest the authors amend the claim it believed to be a pathogen.Also, there are many recent, high quality Listeriareferences which could be used to support general microbiology in your introduction.
Within the genus Listeria, only L. monocytogenesand L. ivanoviiare considered virulent, with L. monocytogenesbeing the only species of public health concern.Listeria innocuais the most frequently encountered nonpathogenic Listeriaspecies.Recently few cases of Listeria innocuainfections has been reported, that why we used the term it believed to be a pathogen.
Due to word limit of case report, we unable to extend the introduction more.
2. At line 51 the patient is referred to as "her".If the patient is a woman, it might better to describe the patient as female in the first line of the case.

Complied in line 59-60
The fluid which was inoculated in Bact Alert FA bottle (bioMerieux Inc, USA) and incubated in Bact Alert which is an automated blood culture incubation instrument at 37 o C.
5. Line 59 "patient was treated conservatively" please include a sentence describing the reasoning for a conservative treatment.This may be useful for future similar cases.Please also provide detail of the dosage of chosen antibiotics.

Complied in Line 65-68
Patient was treated conservatively with a combination of Ampicillin and Gentamicin.On

Date report received: 05 April 2023 Recommendation: Minor Amendment
Comments: In addition to the review comments below, please consider these comments: Listeria is widely accepted as a pathogen.I suggest the authors amend the claim it believed to be a pathogen.Also, there are many recent, high quality Listeria references which could be used to support general microbiology in your introduction.At line 51 the patient is referred to as "her".If the patient is a woman, it might better to describe the patient as female in the first line of the case.Line 52 I suggest changing "total count" to total cell count Please include a brief description of what bact-alert is.Line 59 "patient was treated conservatively" please include a sentence describing the reasoning for a conservative treatment.This may be useful for future similar cases.Please also provide detail of the dosage of chosen antibiotics.Line 62 please also detail the time of second follow-up Table 1: clarity of the table would benefit from the headings being emboldened.Discussion: please reformat so all of the discussion is aligned in the same manner.Line 83 rephrase "less suspected of," to rarely suspected Line 87 change "there is" to there are Abbreviations are used inconsistently throughout.Please ensure to define all abbreviations at the first use.

Please rate the quality of the presentation and structure of the manuscript Satisfactory
To what extent are the conclusions supported by the data?Strongly support

Is there a potential financial or other conflict of interest between yourself and the author(s)? No
If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?Yes Reviewer 1 recommendation and comments https://doi.org/10.1099/acmi.0.000524.v1.4 © 2022 Anonymous.This is an open access peer review report distributed under the terms of the Creative Commons Attribution License.

Anonymous.
Date report received: 04 April 2023 Recommendation: Minor Amendment Comments: This case report is the first case of prosthetic joint infection due to L. innocua for such, it has great scientific value.However, the punctuation, sentence structure, and syntax of some of the paragraphs make it difficult to follow.In general: -The definition of abbreviations should be included when using them for the first time.

Please rate the quality of the presentation and structure of the manuscript Poor
To what extent are the conclusions supported by the data?Strongly support

Is there a potential financial or other conflict of interest between yourself and the author(s)? No
If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?Yes

Complied 3 .Complied 4 .
Line 52 I suggest changing "total count" to total cell count Please include a brief description of what bactalert is.
Figure legends are absent.Please describe the figure in a legend for figure 1. Please italicise all microbial names.
Meningitis and bacteremia caused by Listeria are different clinical manifestations of Listeriosis.Case Presentation: -Consider including a description of the patient's relevant demographic info (without any details that could lead to the identification of the patient).-Please define abbreviations.-Line 39-44: Consider reordering the paragraph (Starting with All relevant medical history of the patient -Include the total knee replacement in the first sentence, and dates when possible.Continue with the symptoms and signs).-Line 44-51: Include dates in the text and reference Table 1.-Line 55: Include the media used for subcultures.-Figure 1: Consider including a detailed explanation of the figure (Figures and tables should be broadly comprehensible without reference to the text).-Table 1: Consider including row/column titles indicating the Visit # (i.e.Visit #1), Date, Symptoms, Exams/Diagnosis, Treatment.Include abbreviations as footnotes.Discussion: -Check grammar, punctuation, syntax, and sentence structure.-Paragraph 1: Check format.-Line 70-72: Check for clarity.Consider re-write the sentence.-Line 74-77: Consider re-write the sentence.It is not accurate and it is very confusing.Listeriosis is not a "rare bacterial disease".Also, sepsis and meningoencephalitis are not causes of listeriosis.-Line 82-85: Consider re-write the sentence.-Line 90-93: Consider re-write the paragraph.

Table 1 .
Timeline of patient follow-up and blood test results

Table 1 :
clarity of the table would benefit from the headings being emboldened.
-Consider using italics for scientific names.-Check grammar, punctuation, syntax, and sentence structure.-Abstract should be included in numeration as #2.Update numeration of subtitles.-Consider combining figure and table under #6.Abstract: -Check grammar, punctuation, syntax, and sentence structure.Introduction: -Line 31-33: Sentence is not correct/clear.1) From Listeria genus only L. monocytogenes and L. ivanovii are considered pathogens; 2)